Tailoring facet sensitivity in anatase titania for selective photocatalytic oxidation of methane to formaldehyde

Photocatalytic methane oxidation is a promising route to produce formaldehyde, yet achieving high efficiency, selectivity, and stability with cost-effective systems remains challenging. Here, we uncover facet sensitivity in the methane photocatalytic oxidation over anatase TiO 2 {001}/{101} junctions. The truncated octahedral bipyramid, exposing 62 % {001} and 38 % {101} facets, exhibits superior photocatalytic performance for methane-to-formaldehyde conversion under ambient conditions. Band structure, carrier dynamics, and mechanistic studies reveal that surface-bound methoxy species (OCH 3 ) act as key intermediates, facilitated by enhanced charge separation and transfer across the {001}/{101} facet junctions. The higher OCH 3 /•OH (hydroxyl radicals) ratio promotes selective methane oxidation to HCHO while suppressing deep oxidation to CO 2 . Furthermore, integration into a microtube reactor with optimized light harvesting and gas–solid–liquid mass transfer boosts performance, achieving a high formaldehyde production rate of 280 mmol g cat −1 h −1 L −1 (2.24 µmol h −1 ) with 100 % selectivity in liquid-phase. This work offers an efficient and scalable approach to catalyst and process engineering for sustainable formaldehyde production via photocatalytic methane conversion. • Facet sensitivity in the methane oxidation over anatase TiO 2 {001}/{101} junctions. • Surface-bound methoxy species (*OCH 3 ) act as key intermediates. • Integration into an optimized microtube reactor boosts the performance. • 100 % formaldehyde selectivity in the liquid phase has been achieved.